Work Package 1:

Development of improved metrological measurement approaches, guidelines and isotope reference materials for NO2, CO2 and CH4 The aim of this work package is to develop improved metrological measurement approaches and guidelines for the harmonisation of field measurements of greenhouse gas isotope ratios by identifying current deficiencies in data accuracy and reliability based on gathering information from laboratories providing isotope certified reference materials (CRMs) for N2O, CO2 and CH4 and the requirements of networks making field-based isotope measurements. Metrological measurement approaches and guidelines for the harmonisation of field measurements are currently lacking. To develop the measurement approaches and guidelines, a review will be made of GHG measurement networks and sites in Europe as well as existing documented measurement procedures and guidelines e.g. WMO, GGMT, IAEA etc. as well as relevant reports from previous projects EMPIR 19ENV05 STELLAR and Partnership 21GRD04 IsoMET and a protocol for laboratory testing of isotope ratio analysers extending established ICOS ATC procedures will be established. The outcome from the review process will be used to develop the first metrological measurement approaches and guidelines for the harmonisation of field measurements of greenhouse gas isotope ratios, like to the ICOS monitoring via measurements in WP3.

Work Package 2:

Improved (testing and validation) metrological measurement methods for field isotope ratios for carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) isotope ratios The aim of this work package is to improve (testing and validation) both optical and mass spectrometric methods and calibration approaches for field measurement of isotope ratios in CO2, CH4 and N2O in support of European and Global measurement networks. The work will build on foundations laid by EMPIR 16ENV06 SIRS, EMPIR 19ENV05 STELLAR and Partnership 21GRD04 isoMET but targeting reduced uncertainties to realise network compatibility goals within the scope of WMO / GAW. In accordance with expert recommendations of GGMT-2022, the project aims to target more stringent compatibility goals for monitoring well-mixed background air at remote stations, and more relaxed goals for regionally focussed studies with large local fluxes, e.g. in urban environments. Compatibility goals represent maximum biases for co-located comparison of measurements at a single site by different techniques. For analytical developments, presented in WP2, the project aims to target analytical uncertainty goals for measurements, which should reach comparable values.

Work Package 3:

Implementation of harmonised measurement approaches for isotope ratio at field sites The aim of this work package is to implement metrological harmonised measurement approaches for GHGs (CO2, CH4, N2O) isotope ratio measurements at field sites, employing the methods (WP2) and guidelines developed in WP1. Instrumentation developed in WP2 will be deployed to existing field measurement sites, e.g. those in the ICOS network, and use calibration reference materials developed in WP1. The measurements will be targeted to the WMO extended compatibility goals of 0.2 ‰ for δ15N and δ18O-N2O, 1 ‰ for δ15NSP, 0.1 ‰ for δ13C-CO2 and δ18O-CO2, 0.2 ‰ for δ13C-CH4 and 5 ‰ for δ2H-CH4. The relative merits of two methods for evaluating measurement compatibility will be evaluated: a round-robin measurement of reference materials and comparison with a co-located reference instrument. The measurement tasks are separated to address the specific instrumental and harmonisation requirements of each species: Task 2.1 will establish the infrastructure for harmonisation of the field measurements; Task 3.2 concerns CO2 isotope ratio measurements, Task 3.3 concerns N2O isotope ratio measurements and Task 3.4 concerns CH4 isotope ratio measurements. Instruments that are validated in activities A2.1.1, A2.2.1 for CO2 and CH4 respectively, and the automated flask sampling system established in A2.3.2, will be deployed to field sites by respective WP3 activities’ participants.

Work Package 4:

Creating impact

Work Package 5:

Management and coordination